Turbo compressor



May 31, 1960 B. ECKERT ETAL 2,938,662

TURBO COMPRESSOR Filed March 16, 1954 INVENTORS BRUNO ECKERT HEINRICH KUHL BY (MD/M61? A ORNEYS United States Patent TURBO COMPRESSOR Bruno Eckert, Stuttgart-Bad Cannstatt, and Heinrich Kuhl, Stuttgart, Germany, assignors to Daimler-Benz Akhengeseilschaft, Stuttgart-Unterturkheim, Germany Filed Mar. 16, 1954, Ser. No. 416,636

Claims priority, application Germany Mar. 24, 1953 6 Claims. (Cl. 230-434) The present invention relates to turbo-engines and more particularly relates to turbo-compressors of the axial flow type which include a rotor and blades mounted radially on the rotor, and wherein the blades are formed as slotted-type blades.

It is accordingly an object of the present invention to provide a turbo-compressor which offers increased efficiency.

It is another object of the present invention to provide a turbo-compressor which permits operation thereof with a greater lift co-efiicient.

It is a still further object of the present invention to provide an axial flow compressor which controls the boundary layer at the blade in such a way as to accelerate the same, thereby preventing separation of the flow of the air from the blade surface. A still further object of the present invention resides in the provision of a slotted blade which permits more efiicient operation of the compressor and which exhibits increased rigidity and strength.

It is a still further object of the present invention to provide an axial flow compressor which produces an increased pressure rise per stage thereof.

A still further object of the present invention resides in the provision of a slotted blade mounted on a rotor of a turbo-compressor which permits the how of the gaseous medium from the high pressure to the low presiure side of the blade to thereby accelerate the boundary ayer.

The adiabatic pressure rise per stage of an axial flow compressor is the greater for a given rotational speed, the greater the lift co-eflicient at the blade. It is a well known expedient to substantially increase the lift co-etficient of a single blade, as well as that of a lattice or row type blade, by an appropriate subdivision of the blade so as to permit the flow of the gaseous medium to pass from the pressure side to the suction side to thereby accelerate the boundary layer which otherwise would tend to separate from the blade surface. Such types of blades or wings are commonly used in connection with airplanes as landing flaps or as slats, in that they are during starting and landing placed into their effective position, while they are rendered inefiective during normal flight. Such use of the landing flaps or slats eliminates the disadvantage of this type of wing or blade, namely, a considerable increase in the resistance during normal flight.

It is also known to use such types of blades in connection with turbo-engines. However, for reasons of the greatly increased losses and because of the great sensitivity to vibrations, the long narrow blades of this type did not prove particularly successful in connection with such use.

The present invention has for its primary purpose the elimination of these disadvantages or difliculties, and consists essentially in that the blade is slotted only over a part thereof, especially near the hub part of the rotor, and does not extend over the entire radial length of the 2,938,662 Patented May 31, 1960 blade. The present invention rests on the following considerations.

In contradistinction to the single wing or blade, as, for example, used in airplanes, the necessary change of direction of the gaseous stream, as, for example, in axial flow compressors, is usually considerably greater at the root or foot of the blade than near the tip of the blade. This is based on the consideration that each part of the blade should produce a substantially equal increase of pressure to avoid currents or flow of undesired components. Since the rotational speed of the bladeis greater at the tip than at the base thereof, it is necessary to have larger lift co-efiicients at the base of the blade than near the tip thereof. Consequently, the curvatureof the blade crosssection at the base must also be greater than at the tip thereof, or diiferently stated, the radius of'curvature must be smaller at the base of the blade than near the tip thereof. This in turn entails a greater danger of separation of flow from the blade surfaces near the hub or rotor part.' It therefore suflices to the limit the slit necessary for the prevention of flow separation to the part of the blade near the rotor or base thereof. In this .manner, the losses, which with the ordinary slot type blade are unavoidable, extend only over a part of the radial blade extent, so that these losses and the decrease in overall efliciency caused thereby is greatly reduced.

The slotted-type blade in accordance with the present invention may be obtained in various ways, as, for example, by providing an auxiliary blade for each main blade, whereby the auxiliary blade may be placed ahead or behind the main blade so as to lead or trail the same. However, a slotted-type blade in accordance with the present invention may be also made possible in that the main blade is provided with a slot in its part near the base thereof, or may consist of two corresponding parts which are connected with each other.

Further objects and advantages in accordance with the present invention will become more obvious from the following description when taken in connection with the accompanying drawing which shows for purposes of illustration only several preferred embodiments in accordance with the present invention, and wherein:

Figure 1 is an elevational view of one preferred embodiment in accordance with the present invention.

Figure 2 is a plan view of the embodiment illustrated in Figure 1. V v

Figure 3 is an elevational view of a modified embodiment in accordance with the present invention.

Figure 4 is a plan view of the modification shown in Figure 3.

Figure 5 is an elevational view of a still further modification in accordance with the resent invention and Figure 6 is a plan view of the modification illustrated in Figure 5.

Referring now more particularly to the drawing, wherein like reference numerals are used throughout the various views to designate like parts thereof, reference numeral 10 designates the turbine motor and reference numeral 11 a main bladeor wing of the turbine. The. part of the blade 11 nearest the rotor 10, i.e. the base thereof, is designated by reference numeral 11, while the part remote from the rotor 10, i.e. the tip thereof, is designated by reference numeral 11". a

In the embodiments illustrated in the drawing, the direction of fiow of the gaseous medium is assumed from the right to the left. As shown in the flow diagrams r and r represent the relative velocities at the inlet and. outlet side of the blade, it represents the circumferential speed of the rotor while a and a represent the absolute velocity to and from the rotor 10. A indicates the direc-' tion of the rotor 10. A leading auxiliary blade 12 precedes the main blade 11 and forms with the leading edge of the main blade a slot 13 in the part thereof near the hub or rotor 10.

As clearly shown in Figure 1, the leading auxiliary blade 12 extends in a radial direction only over a part of the entire length of the main blade, thatis, extends substantially only along that part in the range of which the greatest change of direction of the flow is required.

By making the auxiliary blade 12 only a fraction of the entire length of the main blade 11, the flow losses are reduced by a very considerable amount. Furthermore, the relatively short length of the auxiliary blade 12 is more rigid and is not subjected to large vibrations as would be encountered with such a narrow blade having a length equal to the radial length of the main blade 11.

The modification illustrated in Figs. 3 and 4 is similar to the embodiment of Figs. 1 and 2, but utilizes an auxiliary blade 14 which trails the main blade 11. A slot 15 is formed between the trailing auxiliary blade 14.

Again. it is noted that the auxiliary blade 14 is much shorter in a radial direction than the main blade 11, which offers the advantages fully discussed in connection with the auxiliary blade 12 of Fig. 1.

In each of the embodiments of Figs. 1 and 2, and of Figs. 3 and 4, the slots 13 and 15 are formed byvthe physical separation of the auxiliary blades 12 and 14 from the main blade 11, respectively. It is further noted, that for purposes of efiicient operation of the blade system the leading edge of auxiliary blade 12 slants rearwardly in a radial direction, i.e. the leading edge forms an angle with an imaginary radius, in such a manner that its width is less at the tip thereof than at the base, while the trailing edge of auxiliary blade 12 overlaps with the leading edge of the main blade 11.

Similarly, the trailing edge of the auxiliary blade 14 slopes downwardly in the rearward direction, i.e., the trailing edge forms an angle with an imaginary radius, in such a manner that its width is less at the tip thereof than at the base, while the leading edge of the auxiliary blade overlaps with the trailing edge of the main blade 11.

In the embodiment illustrated in Figs. and 6, the main blade or wing 11 is provided in the part thereof near the rotor with a slot 16 which terminates at a predetermined radial distance from the base 11' thereof.

In comparison with known types of slotted blades or wings, the wings in accordance with the present invention offer simultaneously the advantage of great rigidity, which is obtained in the embodiments of Figs. 1 thru 4 by an auxiliary blade which is considerably shorter than the main blade and in the embodiment of Figs. 5 and 6 by a slot which extends only over a part of the radial length of the main blade and thereby weakens the main blade only relatively little.

It is also possible to make the blades of two parts, such as two similar or complementary parts, which are rigidly connected with each other in any conventional manner, as for example, by welding, soldering, bolts and nuts, rivets, and the like, at points thereof remote from the hub, and which are interconnected thereat without gap or slot.

We claim:

1. A high-speed, axial flow turbo compressor for compressing a fluid medium, in combination, a rotor with an axis of rotation including a hub, main blade means including a leading and a trailing edge and a base secured to said rotor hub, auxiliary blade means including a leading and a trailing edge and a base secured to said rotor hub, said auxiliary blade means being spaced from said main blade means in a plane perpendicular to said axis, said space between said blade means being smaller than the maximum thickness of said main blade means, said 4 fluid medium flowing through said compressor in a substantially axial direction, the leading edge of said auxiliary blade means being disposed ahead of the leading edge of said main blade means while the trailing edge thereof is disposed behind the leading edge of said main blade means in the direction of flow, said main blade means being formed helically in a radial direction thereof, the radial length of said main blade means exceeding the total radial length of said auxiliary blade means.

2. A high-speed, axial flow turbo compressor as set forth in claim 1, wherein said auxiliary blade means has a uniform curvature throughout its radial length.

3. In a high-speed, axial flow turbo compressor as set forth in claim 1, wherein the width of the tips of said main blade means and said auxiliary blade means are less than the Width of the respective bases thereof, and the leading edges of said main blade means and said auxiliary blade means slope downwardly in a trailing direction and forms anacute angle with an imaginary radius.

4. A high-speed, axialflow turbo compressor for compressing a fluid medium, in combination, a rotor with an axis of rotation including a hub, main blade means including a leading and a trailing edge and a base secured to said rotor hub, auxiliary blade means including a leading and a trailing edge and a base secured to said rotor hub, said auxiliary blade means being spaced from said main blade means in a plane perpendicular to said axis, said space between said blade means being smaller than themaximuxn thickness of said main blade means, said fluid medium. flowing through said compressor in a substantially axial direction, the leading edge of said auxiliary blade means being disposed ahead of the trailing edge of said main blade means while the trailing edge thereof is disposed behind the trailing edge of said main blade means in the direction of flow, said main blade means being formed helically in the radial direction thereof, the radial length of said main blade means exceeding the radial total length of said auxiliary blade means.

5. A high-speed, axial flow turbo compressor as set forth in claim 4, wherein said auxiliary blade means has a uniform curvature throughout its radial length.

6. A high-speed, axial flow turbo compressor as set forth in claim 4, wherein the width of the tips of said main blade means and said auxiliary blade means are less than the width of the respective bases thereof, and the leading edges of said main blade means and said auxiliary blade means slope downwardly in a trailing direction and forms an acute angle with an imaginary radius.

References Cited in the file of this patent UNITED STATES PATENTS 1,622,930 Von Karrnan et al'. Mar. 29, 1927 1,724,456 Crook Aug. 13, 1929 1,831,729 Adamtchik Nov. 10, 1931 2,097,389 De Mey et al Oct. 26, 1937 2,135,700 Cievra' Nov. 8, 1938 2,135,887 Fairey Nov. 8, 1938 2,136,403 Vance et al. Nov. 15, 1938 2,166,823 Rosenlocher July 18, 1939 2,180,922 Bothezat Nov. 21, 1939 2,314,572 Chitz Mar. 23, 1943 2,351,516 Jandasek June 13, 1944 2,440,825 Iandasek May 4, 1948 2,650,752 Hoadley Sept. 1, 1953 FOREIGN PATENTS 390,486 Germany Feb. 20, 1924 630,747 Great Britain Oct. 20, 1949 

